Composites of rubber and fiber are used for belts, rubber hoses, diaphragms, and numerous other fields. In the field of belts, there are timing belts for automobile use, poly ribbed belts, lapped belts, V-belts, etc. Usually, they are comprised of woven fabric-shaped base fabrics and rubber. For example, in V-belts, the belts are surrounded by canvas for protection, while in toothed belts, the tooth parts have covering fabric laminated over them.
As the rubber, in the past, the oil resistant rubber of chloroprene rubber or acrylonitrile-butadiene copolymer rubber had mainly been used, but in recent years, to deal with automotive emission regulations, the smaller engine compartments for lightening the weight of automobiles, the closed engine compartments for reducing noise, etc., heat resistance is demanded. For this reason, highly saturated nitrile rubber provided with both heat resistance and oil resistance has come to be used.
In this regard, if using a timing belt as an example, the tooth parts are protected by nylon base fabric, but to raise the bonding force between rubber and the base fabric and to suppress the abrasion due to engagement between the belt and gear, in general, the base fabric has been treated by a solvent-based rubber glue. However, recently, to eliminate environmental pollution due to organic solvents, art for treatment by an aqueous binder which takes the place of treatment by a solvent-based rubber glue has been desired.
As such art for treatment by an aqueous binder, Patent Document 1 discloses an adhesive composition which contains a carboxyl group-containing highly saturated nitrile rubber latex and resorcinol formaldehyde resin. However, along with the higher performance in engine compartments in automobiles, the demands on the materials have become increasingly severe. Further, adhesive compositions which can form adhesive layers which are excellent in mechanical strength, abrasion resistance, and waterproofness have been sought.